1. Field of the Invention
This invention relates to display apparatuses such as display apparatuses for televisions and computers for receiving television signals and image signals of computers etc. and displaying images, and image signal processing apparatuses and drive control apparatuses for them.
More closely, it relates to a display apparatus which compensates a decreased portion of drive voltage resulting from electric resistance that a matrix wiring of a display panel has and effectively applied to display devices, and can drive the display devices with appropriate drive voltage, and an image signal processing apparatus and a drive control apparatus for the same.
2. Description of the Related Art
One of display devices is a cold cathode device. A example of a display apparatus having cold cathode devices is disclosed in JP Patent Publication No. 8-248920 (U.S. Pat. No. 5,734,361 specification). The display apparatus described in this document has such a structure that, in order to compensate lower luminance due to voltage drop by wiring resistance of electric connection wiring to the cold cathode device, its compensation data is calculated by statistical calculation and a desired value of an electron beam and the compensation value are combined.
The structure of the display apparatus described in this document is shown in FIG. 42. The structure involved in the data compensation in the apparatus is approximately as described below.
Firstly, a totalizer 1206 totalizes luminance data of one line of a digital image signal and outputs its totalized value to a memory 1207, and thereby, compensation data corresponding to the totalized value is read out from the memory 1207. On the other hand, the digital image signal is serial-to-parallel converted at a shift register 1204 and held for a predetermined time in a latch circuit 1205, and thereafter, inputted at a predetermined timing to a multiplier 1208 provided with respect to each column wiring. The multiplier 1208 multiplies the luminance data and the compensation data read out from the memory 1207 with respect to each column wiring to generate data after compensation, and transfers this data after compensation to a modulating signal generator 1209. The modulating signal generator 1209 generates a modulating signal corresponding to the data after compensation. Based upon this modulating signal, an image is displayed on a display panel. Here, like totalization processing of the luminance data of an 1 line portion of the digital image signal in the totalizer 1206, statistical calculation processing such as calculating summation and average to the digital image signal is carried out, and based upon this value, compensation is carried out.
However, in case of the conventional compensation for voltage drop, the processing for limitation of electric power which is generally called ABL (Automatic Brightness Limiter) is not carried out.
And, in case of the conventional compensation for voltage drop, signal processing in order to calculate a current of a high voltage power supply (an anode current which is flowing through an anode electrode) precisely is not carried out either.